The present invention relates generally to seals for rotary devices, and more specifically, to a hermetic seal that permits limited rotation of a rotary device.
A device with limited rotation such as a rotary damper has a propensity to leak viscous fluid from its shaft. A primary shaft seal is usually placed over the shaft in order to prevent this viscous fluid leakage. However, the primary shaft seal does not provide a perfect seal around a shaft of the rotary damper, and therefore small amounts of viscous fluid leak out to the external environment. This leaked fluid often is deposited on and causes damage to other instruments in the external environment. For example, with respect to a rotary damper for a space payload, such as a telescope, the leaked fluid may be deposited on optical instruments of the telescope, thereby blurring the output images.
In addition, in other rotary devices, such as vehicle motors, a clean vacuum environment around the rotary device is necessary for proper operation. Fluid or lubrication leakage from a shaft in the rotary device can damage or contaminate other items in the exterior environment.
Therefore, what is needed is a seal for a rotary device that prevents viscous fluid or lubricant (contaminants) from leaking and/or escaping to the external environment and that provides a clean environment around the rotary device.
In view of the above, the present invention provides a hermetic seal for devices with limited rotation. The hermetic seal includes a plurality of vertical convolutes and a plurality of horizontal convolutes. In a first embodiment, the vertical convolutes extend vertically from a device housing to the horizontal convolutes, which extend horizontally around the shaft. The vertical convolutes are bonded to the device housing, and the horizontal convolutes are bonded to the vertical convolutes and to the device shaft. The vertical convolutes stretch to permit limited rotation of the device shaft while still maintaining a barrier. The horizontal convolutes expand and contract to permit the vertical convolutes to fold upon themselves and to accommodate the length changes of the vertical convolutes. In a second embodiment, the horizontal convolutes are mounted to the device housing and the vertical convolutes. The vertical convolutes are mounted to the shaft and to the horizontal convolutes. In a third embodiment, the hermetic seal includes two sets of horizontal convolutes. One of the two sets of horizontal convolutes is mounted to the device housing and the other is mounted to the shaft. The vertical convolutes are mounted to both sets of horizontal convolutes and extend vertically from the first set of horizontal convolutes to the second set of horizontal convolutes.
The present invention consequently provides a hermetic seal for devices with limited rotation that prevents contaminant leakage to the exterior environment while defining a barrier between the device shaft and the device housing.